NEW RESEARCH shows that cacti are surprisingly fast at creating new species.
Biologists have long thought that pollinators and specialised flowers drive the formation of new plant species.
However scientists at the University of Reading have found that in cacti, how quickly flowers change shape is more significant than how big the flowers grow or which animal pollinates them.
Researchers studied flower length data for more than 750 cactus species, covering a 185-fold range in size from just 2mm to 37cm.
Despite this variation, flower length had almost no relationship with how fast a species split into new ones.
Instead, species whose flowers were evolving most rapidly were also the most likely to branch into new species, an effect that held across both recent and deep evolutionary history.
The research was made possible by a new Open Access database called CactEcoDB, created by the study’s lead author Dr Jamie Thompson, and developed in collaboration with ten coauthors from three continents, including six from the University of Reading.
Their study, published today (Wednesday, March 18) in Biology Letters, challenges ideas which date back to Charles Darwin, whose studies of orchids suggested that specialised flower forms drove the creation of new plant species.
Dr Jamie Thompson, lead author at the University of Reading, said: “People may think of cacti as tough, slow-growing plants, but our research shows that the cactus family is one of the fastest-evolving plant groups on Earth.
“Knowing how fast cacti evolve reveals that deserts, often seen as harsh and unchanging, are actually hotbeds of rapid natural change.
“We expected cacti with longer, more specialised flowers to be the ones creating the most new species.
“Instead,” he explains, “flower size made almost no difference. What matters is how quickly flowers change shape.
“Cacti whose flowers evolve rapidly are far more likely to split into new species than those whose flowers stay the same, however elaborate they are.
“This result has real implications for conservation. Since flower evolution has helped generate cactus species over millions of years, evolutionary pace should become part of conservation efforts.”
He continued: “Although being able to rapidly evolve does not guarantee resilience, especially as the planet is changing faster than most cacti can keep up, it could help predict which species need the most help.
“Rather than searching for a single trait that predicts which cacti are most at risk, conservationists may need to look at how fast a species is evolving instead.”
